The present invention relates to a vertical die casting press of the type disclosed in U.S. Pat. Nos. 5,332,026 and 5,660,223 which issued to the assignee of the present invention, and to other forms of vertical die casting presses or apparatus, such as disclosed in U.S. Pat. Nos. 3,866,666 and 4,799,534. In such a press or apparatus, a frame supports one or more vertical shot cylinders or sleeves, and each sleeve receives a shot piston mounted on a shot piston rod connected to a hydraulic cylinder. The shot sleeve receives a molten die casting metal which is forced upwardly by the shot piston into a die cavity defined between a vertically moveable upper die member and a lower plate or die member. The lower die member defines a gate opening through which the metal within the shot sleeve is forced upwardly into the die cavity to form a die cast part. As shown in the above ""026 Patent, after the molten metal has cooled within the die cavity, the upper die member is unclamped and elevated, and the lower die member is shifted laterally or horizontally to a station where the part is removed from the lower die member. The remaining solidified metal or biscuit within the shot sleeve is removed by elevating the shot piston and pressing the biscuit laterally from the shot piston. When multiple shot sleeves are used in the press, the shot sleeves are indexed between a metal receiving station and a metal injection or transfer station, for example, as disclosed in above ""223 Patent.
It has been determined that a vertical die casting press may be constructed and used for efficiently and effectively producing a high quality fiber reinforced metal part, such as an aluminum or magnesium part having high strength and stiffness where desired, and also a high strength/weight ratio. For example, a C-shaped brake caliper housing for a motor vehicle is commonly produced from cast iron in order to obtain the necessary strength. However, with a die casting press constructed and used in accordance with the present invention, a high quality die cast fiber reinforced aluminum brake caliper housing may be efficiently produced with the necessary strength and stiffness and with the important advantage of a significant reduction in weight. Other high quality fiber reinforced aluminum and magnesium parts may also be efficiently produced with the apparatus and method of the invention.
The present invention is directed to an improved vertical die casting apparatus or press and a method of die casting light weight metal parts, and which is ideally suited for die casting fiber reinforced aluminum and magnesium parts having a high strength/weight ratio and a high stiffness. The press and method of the invention is also effective to produce light weight metal parts without the inclusion of solid metal particles and with effective infiltration of porous and fibrous reinforcing preforms within the part.
In accordance with a preferred embodiment of the invention, a vertical die casting press includes a water cooled shot sleeve which receives a vertically moveable water cooled shot piston connected by a piston rod to a hydraulic cylinder. The shot sleeve and shot piston define a cylindrical shot chamber under a lower gate plate or die member which cooperates with a vertically moveable upper die member to define a die cavity corresponding to the part to be die cast. The lower gate plate or die member defines a gate opening within a center portion of the shot chamber, and the diameter of the shot sleeve is at least three times the width or diameter of the gate opening, and preferably greater. The lower die member also defines an annular metal entrapment cavity or recess aligned with the inner surface of the shot sleeve, and relatively deep air vent slots extend laterally outwardly from the entrapment recess within the lower mold die member.
A vertical die casting press of the invention is ideally suited for die casting fiber reinforced aluminum and magnesium parts, and the reinforcing fibers are positioned within the die cavity by a porous preform located within the die cavity where high tensile strength and stiffness is required in the die cast part. After molten metal, such as aluminum or magnesium, is poured or inserted into the shot chamber, and the upper and lower die members are positioned and clamped above the shot sleeve, the molten metal is forced upwardly by the shot piston through the center gate opening and into the die cavity. As the shot piston moves upwardly within the shot sleeve, the pre-solidified metal shell adjacent the shot sleeve collapses, and the upper portion of the shell is forced into the entrapment recess. The displaced air above the molten metal within the shot sleeve flows outwardly through the radial vent slots which are then closed by the collapsing shell of pre-solidified metal. Thus only the highest quality molten metal from the center portion of the shot chamber flows upwardly through the gate opening into the die cavity to infiltrate the porous preform with the reinforcing fibers.
Other features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.